/*====================================================================*
 *
 *   fcs.c - ethernet frame check sequence functions
 *
 *   see http://www.csm.ornl.gov/~dunigan/crc.html for an explanation
 *   of the CRC-32 algorithm reportedly used by PKZip, Ethernet, FDDI
 *   and other popular protocols for error detection;
 *
 *   Motley Tools by Charles Maier;
 *   Copyright (c) 2001-2006 by Charles Maier Associates;
 *   Licensed under the Internet Software Consortium License;
 *
 *--------------------------------------------------------------------*/

#ifndef FCS_SOURCE
#define FCS_SOURCE

/*====================================================================*
 * system header files;
 *--------------------------------------------------------------------*/

#include <stdint.h>

/*====================================================================*
 * variables;
 *--------------------------------------------------------------------*/

static uint32_t CRCTable [256] =

{
	0x00000000,
	0x77073096,
	0xee0e612c,
	0x990951ba,
	0x076dc419,
	0x706af48f,
	0xe963a535,
	0x9e6495a3,
	0x0edb8832,
	0x79dcb8a4,
	0xe0d5e91e,
	0x97d2d988,
	0x09b64c2b,
	0x7eb17cbd,
	0xe7b82d07,
	0x90bf1d91,
	0x1db71064,
	0x6ab020f2,
	0xf3b97148,
	0x84be41de,
	0x1adad47d,
	0x6ddde4eb,
	0xf4d4b551,
	0x83d385c7,
	0x136c9856,
	0x646ba8c0,
	0xfd62f97a,
	0x8a65c9ec,
	0x14015c4f,
	0x63066cd9,
	0xfa0f3d63,
	0x8d080df5,
	0x3b6e20c8,
	0x4c69105e,
	0xd56041e4,
	0xa2677172,
	0x3c03e4d1,
	0x4b04d447,
	0xd20d85fd,
	0xa50ab56b,
	0x35b5a8fa,
	0x42b2986c,
	0xdbbbc9d6,
	0xacbcf940,
	0x32d86ce3,
	0x45df5c75,
	0xdcd60dcf,
	0xabd13d59,
	0x26d930ac,
	0x51de003a,
	0xc8d75180,
	0xbfd06116,
	0x21b4f4b5,
	0x56b3c423,
	0xcfba9599,
	0xb8bda50f,
	0x2802b89e,
	0x5f058808,
	0xc60cd9b2,
	0xb10be924,
	0x2f6f7c87,
	0x58684c11,
	0xc1611dab,
	0xb6662d3d,
	0x76dc4190,
	0x01db7106,
	0x98d220bc,
	0xefd5102a,
	0x71b18589,
	0x06b6b51f,
	0x9fbfe4a5,
	0xe8b8d433,
	0x7807c9a2,
	0x0f00f934,
	0x9609a88e,
	0xe10e9818,
	0x7f6a0dbb,
	0x086d3d2d,
	0x91646c97,
	0xe6635c01,
	0x6b6b51f4,
	0x1c6c6162,
	0x856530d8,
	0xf262004e,
	0x6c0695ed,
	0x1b01a57b,
	0x8208f4c1,
	0xf50fc457,
	0x65b0d9c6,
	0x12b7e950,
	0x8bbeb8ea,
	0xfcb9887c,
	0x62dd1ddf,
	0x15da2d49,
	0x8cd37cf3,
	0xfbd44c65,
	0x4db26158,
	0x3ab551ce,
	0xa3bc0074,
	0xd4bb30e2,
	0x4adfa541,
	0x3dd895d7,
	0xa4d1c46d,
	0xd3d6f4fb,
	0x4369e96a,
	0x346ed9fc,
	0xad678846,
	0xda60b8d0,
	0x44042d73,
	0x33031de5,
	0xaa0a4c5f,
	0xdd0d7cc9,
	0x5005713c,
	0x270241aa,
	0xbe0b1010,
	0xc90c2086,
	0x5768b525,
	0x206f85b3,
	0xb966d409,
	0xce61e49f,
	0x5edef90e,
	0x29d9c998,
	0xb0d09822,
	0xc7d7a8b4,
	0x59b33d17,
	0x2eb40d81,
	0xb7bd5c3b,
	0xc0ba6cad,
	0xedb88320,
	0x9abfb3b6,
	0x03b6e20c,
	0x74b1d29a,
	0xead54739,
	0x9dd277af,
	0x04db2615,
	0x73dc1683,
	0xe3630b12,
	0x94643b84,
	0x0d6d6a3e,
	0x7a6a5aa8,
	0xe40ecf0b,
	0x9309ff9d,
	0x0a00ae27,
	0x7d079eb1,
	0xf00f9344,
	0x8708a3d2,
	0x1e01f268,
	0x6906c2fe,
	0xf762575d,
	0x806567cb,
	0x196c3671,
	0x6e6b06e7,
	0xfed41b76,
	0x89d32be0,
	0x10da7a5a,
	0x67dd4acc,
	0xf9b9df6f,
	0x8ebeeff9,
	0x17b7be43,
	0x60b08ed5,
	0xd6d6a3e8,
	0xa1d1937e,
	0x38d8c2c4,
	0x4fdff252,
	0xd1bb67f1,
	0xa6bc5767,
	0x3fb506dd,
	0x48b2364b,
	0xd80d2bda,
	0xaf0a1b4c,
	0x36034af6,
	0x41047a60,
	0xdf60efc3,
	0xa867df55,
	0x316e8eef,
	0x4669be79,
	0xcb61b38c,
	0xbc66831a,
	0x256fd2a0,
	0x5268e236,
	0xcc0c7795,
	0xbb0b4703,
	0x220216b9,
	0x5505262f,
	0xc5ba3bbe,
	0xb2bd0b28,
	0x2bb45a92,
	0x5cb36a04,
	0xc2d7ffa7,
	0xb5d0cf31,
	0x2cd99e8b,
	0x5bdeae1d,
	0x9b64c2b0,
	0xec63f226,
	0x756aa39c,
	0x026d930a,
	0x9c0906a9,
	0xeb0e363f,
	0x72076785,
	0x05005713,
	0x95bf4a82,
	0xe2b87a14,
	0x7bb12bae,
	0x0cb61b38,
	0x92d28e9b,
	0xe5d5be0d,
	0x7cdcefb7,
	0x0bdbdf21,
	0x86d3d2d4,
	0xf1d4e242,
	0x68ddb3f8,
	0x1fda836e,
	0x81be16cd,
	0xf6b9265b,
	0x6fb077e1,
	0x18b74777,
	0x88085ae6,
	0xff0f6a70,
	0x66063bca,
	0x11010b5c,
	0x8f659eff,
	0xf862ae69,
	0x616bffd3,
	0x166ccf45,
	0xa00ae278,
	0xd70dd2ee,
	0x4e048354,
	0x3903b3c2,
	0xa7672661,
	0xd06016f7,
	0x4969474d,
	0x3e6e77db,
	0xaed16a4a,
	0xd9d65adc,
	0x40df0b66,
	0x37d83bf0,
	0xa9bcae53,
	0xdebb9ec5,
	0x47b2cf7f,
	0x30b5ffe9,
	0xbdbdf21c,
	0xcabac28a,
	0x53b39330,
	0x24b4a3a6,
	0xbad03605,
	0xcdd70693,
	0x54de5729,
	0x23d967bf,
	0xb3667a2e,
	0xc4614ab8,
	0x5d681b02,
	0x2a6f2b94,
	0xb40bbe37,
	0xc30c8ea1,
	0x5a05df1b,
	0x2d02ef8d
};


/*====================================================================*
 *
 *   uint32_t ReflectBits (uint32_t value, uint32_t bits);
 *
 *   return the bitwise mirror image of an integer value;
 *
 *   Motley Tools by Charles Maier;
 *   Copyright (c) 2001-2006 by Charles Maier Associates;
 *   Licensed under the Internet Software Consortium License;
 *
 *--------------------------------------------------------------------*/

#if 0

static uint32_t ReflectBits (uint32_t value, uint32_t bits)

{
	uint32_t image = 0;
	uint32_t bit;
	for (bit = 0; bit < bits; bit++)
	{
		if (value & 1)
		{
			image |= 1 << (bits - bit - 1);
		}
		value >>= 1;
	}
	return (image);
}


#endif

/*====================================================================*
 *
 *   void InitCRCTable (void);
 *
 *   write frame control sequence table with values; this function is
 *   only needed to populate an empty CRCTable;
 *
 *   Motley Tools by Charles Maier;
 *   Copyright (c) 2001-2006 by Charles Maier Associates;
 *   Licensed under the Internet Software Consortium License;
 *
 *--------------------------------------------------------------------*/

#if 0

static void InitCRCTable (uint32_t CRCTable [])

{
	extern uint32_t CRCTable [];
	uint32_t word;
	uint32_t bit;
	for (word = 0; word < 256; word++)
	{
		uint32_t crc = ReflectBits (word, 8) << 24;
		for (bit = 0; bit < 8; bit++)
		{
			crc = (crc << 1) ^ ((crc & 0x80000000)? 0x04c11db7: 0);
		}
		CRCTable [word] = ReflectBits (crc, 32);
	}
	return;
}


#endif

/*====================================================================*
 *
 *   uint32_t ComputeCRC (uint8_t buffer [], uint32_t length);
 *
 *
 *
 *   Motley Tools by Charles Maier;
 *   Copyright (c) 2001-2006 by Charles Maier Associates;
 *   Licensed under the Internet Software Consortium License;
 *
 *--------------------------------------------------------------------*/

uint32_t ComputeCRC (uint8_t buffer [], uint32_t length)

{
	extern uint32_t CRCTable [];
	uint32_t crc = ~0;
	while (length--)
	{
		crc = (crc >> 8) ^ CRCTable [(crc & 0xff) ^ *buffer++];
	}
	return (~crc);
}


/*====================================================================*
 *
 *   int VerifyCRC (uint8_t buffer [], uint32_t length, uint32_t crc);
 *
 *
 *
 *   Motley Tools by Charles Maier;
 *   Copyright (c) 2001-2006 by Charles Maier Associates;
 *   Licensed under the Internet Software Consortium License;
 *
 *--------------------------------------------------------------------*/

int VerifyCRC (uint8_t buffer [], uint32_t length, uint32_t crc)

{
	return (crc = ComputeCRC (buffer, length));
}


/*====================================================================*
 *
 *   int main (int argc, const char * argv [])
 *
 *
 *   Motley Tools by Charles Maier;
 *   Copyright (c) 2001-2006 by Charles Maier Associates;
 *   Licensed under the Internet Software Consortium License;
 *
 *--------------------------------------------------------------------*/

#if 0
#include <stdio.h>

static uint8_t frame [192]=

{
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x01,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x02,
	0x08,
	0x00,
	0x45,
	0x60,
	0x00,
	0xAE,
	0x00,
	0x00,
	0x40,
	0x00,
	0x40,
	0x11,
	0xDF,
	0xB9,
	0xAC,
	0x11,
	0x01,
	0x02,
	0xAC,
	0x11,
	0x01,
	0x01,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x9A,
	0xA4,
	0x94,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00,
	0x00
};

int main (int argc, const char * argv [])

{
	uint32_t size = sizeof (frame);
	uint32_t word;
	uint8_t blah [] =
	{
		0x00,
		0xB0,
		0x52,
		0x11,
		0x22,
		0x33,
		0x00,
		0x0A,
		0x5E,
		0x5A,
		0x27,
		0x38,
		0x88,
		0xE1,
		0x00,
		0x28,
		0xA0,
		0x00,
		0xB0,
		0x52,
		0x02
	};
	while (size > 160)
	{
		word = ComputeCRC (frame, size);
		printf ("%d %08X\n", size, word);
		size -= sizeof (word);
	}
	size = 21;
	word = ComputeCRC (blah, size);
	printf ("%d %08X\n", size, word);
	return (0);
}


#endif

/*====================================================================*
 *
 *--------------------------------------------------------------------*/

#endif

